Find string and delete line - Node.JS

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How to read file, search for string and delete line in node.js? I have tried 

var fs = require('fs')
fs.readFile('shuffle.txt', function read(err, data) {
if (err) {
throw err;
}

lastIndex = function(){
for (var i = data_array.length - 1; i > -1; i--)
if (data_array[i].match('user1'))
return i;
}()

delete data_array[lastIndex];

});
fs node.js search file string
1 Answers

Let's say we have a text file, shuffle.txt contains the following content

john
doe
user1 
some keyword
last word

Now we read the shuffle.txt file and then search for 'user1' keyword. If any line contains the 'user1', then we will remove the line.

var fs = require('fs')
fs.readFile('shuffle.txt', {encoding: 'utf-8'}, function(err, data) {
    if (err) throw error;

    let dataArray = data.split('\n'); // convert file data in an array
    const searchKeyword = 'user1'; // we are looking for a line, contains, key word 'user1' in the file
    let lastIndex = -1; // let say, we have not found the keyword

    for (let index=0; index<dataArray.length; index++) {
        if (dataArray[index].includes(searchKeyword)) { // check if a line contains the 'user1' keyword
            lastIndex = index; // found a line includes a 'user1' keyword
            break; 
        }
    }

    dataArray.splice(lastIndex, 1); // remove the keyword 'user1' from the data Array

    // UPDATE FILE WITH NEW DATA
    // IN CASE YOU WANT TO UPDATE THE CONTENT IN YOUR FILE
    // THIS WILL REMOVE THE LINE CONTAINS 'user1' IN YOUR shuffle.txt FILE
    const updatedData = dataArray.join('\n');
    fs.writeFile('shuffle.txt', updatedData, (err) => {
        if (err) throw err;
        console.log ('Successfully updated the file data');
    });

});

Here, if a line contains 'user1' keyword, we are removing the entire line. The new shuffle.txt file will be no longer contains a line with 'user1' keyword. The updated shuffle.txt file looks like

john
doe
some keyword
last word

For more information check the doc.

user_53616460
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